Transmissions for powered vehicles transfer torque output by the vehicle's drive unit to one or more loads. In some transmissions, a ratio varying unit (“variator”) is used to provide a continuous variation of transmission ratio rather than a series of predetermined ratios. The variator is coupled between the transmission input and the transmission output via gearing and one or more clutches.
Continuously variable transmissions may have multiple operating modes, where each operating mode covers a portion of the overall ratio spread of the transmission. Each operating mode is selectable, e.g. by a clutch that is engaged by the application of hydraulic fluid pressure as commanded by the transmission's control unit.
Some continuously variable transmissions have a “geared neutral” mode, in which the continuous variation of ratio passes through the geared neutral mode in transitioning from a reverse ratio to a forward ratio. In the geared neutral position, the vehicle's speed is zero, independently of the rotational speed output by the vehicle's drive unit. Transmissions that have a geared neutral mode may be referred to as infinitely variable transmissions.